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Indirect effect of conjugate pneumococcal vaccination in a 2+1 dose schedule

Didrik F Vestrheim1, E Arne Høiby1, Marianne R Bergsaker1

  • 1Division of Infectious Disease Control, Norwegian Institute of Public Health, Oslo, Norway.

Vaccine
|January 9, 2010
PubMed

Insights

The heptavalent pneumococcal conjugate vaccine (PCV7) significantly reduced invasive pneumococcal disease (IPD) across all ages in Norway. The vaccine demonstrated high effectiveness, even in unvaccinated individuals, highlighting herd immunity benefits.

Area of Science:

  • * Public Health
  • * Vaccinology
  • * Epidemiology

Background:

  • * The heptavalent pneumococcal conjugate vaccine (PCV7) was implemented in the Norwegian national immunization program in 2006 using a 2+1 dose schedule.
  • * This study assessed changes in invasive pneumococcal disease (IPD) incidence from 2004-2005 to 2008, focusing on indirect protection in unvaccinated populations.

Purpose of the Study:

  • * To evaluate the impact of PCV7 introduction on IPD incidence in all age groups.
  • * To determine the indirect protective effect of PCV7 vaccination on unvaccinated individuals.

Main Methods:

  • * Retrospective analysis of IPD incidence data before and after PCV7 introduction.
  • * Comparison of disease rates across different age groups and vaccination status.
  • * Assessment of serotype-specific IPD trends.

Main Results:

  • * Significant declines in IPD caused by PCV7 serotypes were observed across multiple age groups, including <5, 5-19, 40-64, and ≥65 years.
  • * The unvaccinated population aged ≥5 years experienced a 48% reduction in PCV7-serotype IPD, contributing to 74% of all prevented cases in 2008.
  • * An increase in IPD caused by non-PCV7 serotypes was noted in adults aged ≥65 years.

Conclusions:

  • * The 2+1 dose schedule of PCV7 vaccination demonstrated very high effectiveness.
  • * Significant indirect protection against IPD was observed in the unvaccinated population, underscoring herd immunity.
  • * Emergence of non-vaccine serotypes in older adults warrants continued surveillance.

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